摘要:

We have established a new convergent scheme to treat analytically nucleon‐nucleon interactions from a chiral effective field theory. The Kaplan‐Savage‐Wise (KSW) amplitudes are resummed to fulfill the unitarity or right hand cut to all orders below pion production threshold. This is achieved by matching order by order in the KSW power counting the general expression of a partial wave amplitude with resummed unitarity cut, with the inverses of the KSW amplitudes. As a result, a new convergent and systematic KSW expansion is derived for an on‐shell interacting kernelRin terms of which the partial waves amplitudes are computed. The agreement with data for the S‐waves is fairly good up to laboratory energies around 350 MeV and clearly improves and reestablishes the phenomenological success of the KSW amplitudes when treated within this scheme. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570565

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We study how far the Index Theorem can be extrapolated from the continuum to finite lattices with finite topological charge densities. To examine how the Wilson action approximates the Index theorem, we specialize in the lattice version of the Schwinger model. We propose a new criterion for solutions of the Ginsparg‐Wilson Relation constructed with the Wilson action. We conclude that the Neuberger action is the simplest one that maximally complies with the Index Theorem, and that its best parameter ind= 2 ism0= 1.1 ± 0.1. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570566

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Effective field theory requires all observables to be independent of the representation used for the quantum field operators. Off‐shell parts of the in‐medium vertex functions depend on the partucular representation so that off‐shell properties of the interactions should not lead to any observable effects. We analyse this issue in the context of many‐body approaches to nuclear matter, where it should be possible to shift into three‐body force the contributions from purely off‐shell two‐body interactions. We show that none of the commonly used truncations of the two‐body scattering amplitude such as the ladder, Brueckner‐Hartree‐Fock or parquet approximations respect this requirement. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570567

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We report on our recent work about the description of a meson gas below the chiral phase transition within the framework of Chiral Perturbation Theory. As an alternative to the standard treatment, we present a calculation of the quark condensate which combines the virial expansion and the meson‐meson scattering data. We have also calculated the full one‐loop elastic pion scattering amplitude at finite temperature and we have unitarized the amplitude using the Inverse Amplitude Method in order to reproduce the temperature effects on the mass and width of the &rgr; and &sgr; resonances. Our results show a clear increase of the thermal &rgr; width, as expected from previous analysis. The results for the &sgr; are consistent with Chiral Symmetry Restoration. We comment on the relevance of our results within the context of Relativistic Heavy Ion Collisions. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570568

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

By using thermal QCD sum rules to investigate the &thgr;¯ induced neutron electric dipole momentdn, we have examined the behaviour of broken CP symmetry at finite temperature. We find that, below the critical temperature, the ratio| dn&thgr;¯ |slightly decreases but survives at temperature effects, implying T nonrestoration of CP‐invariance [1]. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570569

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A simple thermal model with single freeze‐out and flow is used to analyze the ratios of hadron yields and the hadron transverse‐mass spectra measured insNN = 130 GeVAu+Au collisions at RHIC. An overall very good agreement between the model predictions and the data is achieved for all measured hadron species including hyperons. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570570

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We continue the analysis of the preceding talk with a discussion of the elliptic flow and the Hanbury‐Brown‐Twiss pion correlation radii. It is shown that the thermal model can be extended to describe these phenomena. The description of the elliptic flow involves an appropriate deformation of the freeze‐out hyper‐surface and flow velocity. The obtained results agree reasonably with the data for soft (< 2 GeV) transverse momenta. For the pionic HBT correlation radii the experimental feature thatRout/Rside≃ 1 is naturally obtained. The reproduction of individualRsideandRoutcan be achieved with the inclusion of the excluded volume corrections, which effectively increase the radii by ∼ 30&percent;. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570571

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We discuss the possible phase structure of strongly interacting matter in the regime of high densities and low temperatures where the quarks are expected to be in a color superconducting state. We focus on the additional constraints imposed by the requirement of electric and color neutrality which is essential for the description of neutron star interiors. To that end we employ a 3‐flavor NJL‐type quark model, which treats the diquark condensates and the quark‐antiquark condensates on an equal footing. The resulting phase diagram at zero temperature and the various independent chemical potentials turns out to be very rich, containing at least five different color superconducting phases. We search for regions of electrically and color neutral matter and also discuss the possibility of mixed phases with zero net charge. Neglecting surface and Coulomb effects we find nine different mixed phases with up to four components. Preliminary estimates indicate, however, that the mixed phases become unstable if surface and Coulomb effects are included. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570572

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the form factors of the interaction on the phase diagram of quark matter under the condition of &bgr;‐ equilibrium and charge neutrality. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state. We calculate the quark star configurations by solving the Tolman‐ Oppenheimer‐ Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of &Dgr;Mc2∼ 1053erg. We study the consequences of antineutrino trapping in hot quark matter for quark star configurations with possible diquark condensation and discuss the claim that this energy could serve as an engine for explosive phenomena. A “phase diagram” for rotating compact stars (angular velocity‐baryon mass plane) is suggested as a heuristic tool for obtaining constraints on the equation of state of QCD at high densities. It has a critical line dividing hadronic from quark core stars which is correlated with a local maximum of the moment of inertia and can thus be subject to experimental verification by observation of the rotational behavior of accreting compact stars. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570573

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The effects of the &rgr; − &ohgr; mixing term in infinite nuclear matter and in finite nuclei are investigated with the non‐linear Walecka model in a Thomas‐Fermi approximation. For infinite nuclear matter the influence of the mixing term in the binding energy calculated with the NL3 and TM1 parametrizations can be neglected. Its influence on the symmetry energy is only felt for the TM1 with a unrealistically large value for the mixing term strength. For finite nuclei the contribution of the isospin mixing term is very large as compared with the expected value to solve the Nolen‐Schiffer anomaly. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570574

出版商:AIP    

年代:1903

数据来源: AIP